How to send an email using command line? [duplicate]

First of all you need to install and configure Postfix to Use Gmail SMTP on Ubuntu.

Install all necessary packages:

$ sudo apt-get install postfix mailutils libsasl2-2 ca-certificates libsasl2-modules

If you do not have postfix installed before, postfix configuration wizard will ask you some questions. Just select your server as Internet Site and for FQDN use something like mail.example.com

Then open your postfix config file:

$ sudo -H gedit /etc/postfix/main.cf

and add following lines to it:

relayhost = [smtp.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_CAfile = /etc/postfix/cacert.pem
smtp_use_tls = yes

You might have noticed that we haven’t specified our Gmail username and password in above lines. They will go into a different file. Open/Create:

$ sudo -H gedit /etc/postfix/sasl_passwd

And add following line:

[smtp.gmail.com]:587    [email protected]:PASSWORD

If you want to use your Google App’s domain, please replace @gmail.com with your @domain.com.

Fix permission and update postfix config to use sasl_passwd file:

$ sudo chmod 400 /etc/postfix/sasl_passwd
$ sudo postmap /etc/postfix/sasl_passwd

Next, validate certificates to avoid running into error. Just run following command:

$ cat /etc/ssl/certs/Thawte_Premium_Server_CA.pem | sudo tee -a /etc/postfix/cacert.pem

Finally, reload postfix config for changes to take effect:

$ sudo /etc/init.d/postfix reload

Testing

Check if mails are sent via Gmail SMTP server

If you have configured everything correctly, following command should generate a test mail from your server to your mailbox.

echo "Test mail from postfix" | mail -s "Test Postfix" [email protected]

To further verify, if mail sent from above command is actually sent via Gmail’s SMTP server, you can log into Gmail account [email protected] with PASSWORD and check "Sent Mail" folder in that Gmail account. By default, Gmail always keeps a copy of mail being sent through its web-interface as well as SMTP server. This logging is one strong reason that we often use Gmail when mail delivery is critical.

Troubleshooting

Error: "SASL authentication failed; server smtp.gmail.com"

You need to unlock the captcha by visiting this page https://www.google.com/accounts/DisplayUnlockCaptcha

You can run test again after unlocking captcha.
source

you can install mutt via this command:

$ sudo apt-get install mutt

Using mail

mail -s "TestSubject" [email protected] -a "UserReport.txt"  < MessageBody.txt

Using mutt

mutt -s "TestSubject" [email protected] -a "UserReport.txt"  < MessageBody.txt

While UserReport.txt is your attachment file, MessageBody is text/file of your body of email, TestSubject is your email subject.

-s flag is used for "Subject" and -a flag is used for "Attachment file"

Your line could look in shortest way like in this little shell-script:

#!/bin/bash
cat email.txt && sendmail [email protected] < /tmp/email.txt

UPDATED MANY YEARS LATER: Working on Ubuntu 16

1. Allow "less secure apps" to connect to your Gmail by following this link:

   https://myaccount.google.com/lesssecureapps?pli=1
   

2. Run the following commands:

   sudo update-ca-certificates
   sudo apt-get install msmtp-mta
   nano ~/.msmtprc
   

3. Set the following msmtp config (replace [email protected], yourUsername and yourPassword):

   account gmail
   auth on
   host smtp.gmail.com
   port 587
   auth on
   tls on
   tls_trust_file /etc/ssl/certs/ca-certificates.crt
   from [email protected]
   user yourUsername
   password yourPassword
   
   account default : gmail
   

4. Config mail to use msmtp:

   nano ~/.mailrc
   

5. Paste this:

   set sendmail="/usr/bin/msmtp"
   

6. Finally send your mail (replace [email protected]):

   echo hello | mail -s test [email protected]
   

7. Alternative you can use "mailx" to even send attachments easily:

   echo "mail body" | mailx -a /path/to/your/file.doc -s "mail subject" [email protected]